Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$151.45	3.704%	$157.0597	$157.06	$157.05	$157.10
Purchase #2	$160.54	11.744%	$179.3938	$179.39	$179.40	$179.40
Purchase #3	$164.97	6.218%	$175.2278	$175.23	$175.25	$175.20
Purchase #4	$164.95	11.822%	$184.4504	$184.45	$184.45	$184.50
Purchase #5	$117.65	12.639%	$132.5198	$132.52	$132.50	$132.50
Purchase #6	$42.61	11.474%	$47.4991	$47.50	$47.50	$47.50
Purchase #7	$209.70	6.244%	$222.7937	$222.79	$222.80	$222.80
7 purchase totals =	$1,011.87		$1,098.9443	$1,098.94	$1,098.95	$1,099.00